1. Field of the Invention
The present invention relates generally to aircraft electrical systems. More particularly, it relates to an improved method and apparatus for protecting aircraft electrical systems from lightning strikes.
2. Description of Related Art
Aircrafts typically include some form of antenna and electronic communication system for receiving and distributing throughout the aircraft, electronic communications such as navigational and air-traffic control information. In addition to traditional aircraft communication systems, the assignee of the present invention has developed aircraft communication systems that allow direct broadcast satellite television signals to be received and distributed on-board an in-flight aircraft. The above-referenced system includes generally an in-flight entertainment system that incorporates a satellite signal receiver station. The in-flight receiver station receives television signals broadcast from a satellite, and the aircraft's signal distribution system distributes the received television programming to passengers. Various aspects of the above-referenced system are disclosed in several co-pending U.S. patent applications, including application Ser. No. 08/667,222, filed Jun. 19, 1996, entitled "Aircraft Satellite Television System for Distributing Television Programming Derived From Direct Broadcast Satellites" having a patent number 5,790,175 application Ser. No. 08/667,225, filed Jun. 19, 1996, entitled "Distribution Of A Large Number Of Live Television Programs To Individual Passengers In An Aircraft"; now U.S. Pat. No. 5,760,819 and application Ser. No. 08/662,224, filed Jun. 19, 1996, entitled "Distribution Of Satellite Television Programs To Passengers In An Aircraft When It Is Out Of Range Of The Satellites" now U.S. Pat. No. 5,801,751. The entire disclosures of the above-referenced co-pending patent applications are incorporated herein by reference, in their entirety.
Antennas connected to an aircraft, including specifically antennas of the above-referenced communication systems, are typically enclosed in a protective plastic shell housing known generally as a "radome". Radomes are made from a plastic material that protects the antenna from environmental elements while passing the frequencies of the signals being received or transmitted by the antenna. Radomes, however, are susceptible to lightning strikes. A lightning strike hitting the radome could result in damage to equipment within the radome, as well as other downstream equipment connected to the radome-enclosed equipment by wires. In many cases, the downstream equipment is a flight-critical component such as navigational equipment.
One approach to protecting radomes from lightning strikes is to attach lightning protection strips or rods to the radome. The lightning protection strips tend to divert the energy of the lightning strike away from the radome and into the aircraft structure. This approach, however, is not always practical when the equipment enclosed within the radome is a communication antenna because the lightning protection strips tend to degrade the transparency of the radome to the frequencies being received and/or transmitted by the antenna.
Accordingly, there is a need for a method and apparatus that protects radomes and associated equipment from the effects of lightning strikes without degrading antenna performance.